Optimization and quality control of suspended particulate matter concentration measurement using turbidity measurements

The dry weight concentration of suspended particulate material, [SPM] (units: mg L-1), is measured by passing a known volume of seawater through a preweighed filter and reweighing the filter after drying. This is apparently a simple procedure, but accuracy and precision of [SPM] measurements vary widely depending on the measurement protocol and experience and skills of the person filtering. We show that measurements of turbidity, T (units: FNU), which are low cost, simple, and fast, can be used to optimally set the filtration volume, to detect problems with the mixing of the sample during subsampling, and to quality control [SPM]. A relationship between T and 'optimal filtration volume', V opt, is established where V opt is the volume at which enough matter is retained by the filter for precise measurement, but not so much that the filter clogs. This relationship is based on an assessment of procedural uncertainties in the [SPM] measurement protocol, including salt retention, filter preparation, weighing, and handling, and on a value for minimum relative precision for replicates. The effect of filtration volume on the precision of [SPM] measurement is investigated by filtering volumes of seawater ranging between one fifth and twice V opt. It is shown that filtrations at V opt maximize precision and cost effectiveness of [SPM]. Finally, the 90% prediction bounds of the T versus [SPM] regression allow the quality control of [SPM] determinations. In conclusion it is recommended that existing [SPM] gravimetric measurements be refined to include measurement of turbidity to improve their precision and quality control.

[1]  G O Kirst,et al.  Salinity Tolerance of Eukaryotic Marine Algae , 1990 .

[2]  R. W. Sheldon,et al.  SIZE SEPARATION OF MARINE SESTON BY MEMBRANE AND GLASS‐FIBER FILTERS1 , 1972 .

[3]  B. Logan Theoretical analysis of size distributions determined with screens and filters , 1993 .

[4]  D. Spencer,et al.  Marine particles: Analysis and Characterization , 1991 .

[5]  R. W. Austin,et al.  Ocean Optics Protocols for Satellite Ocean Color Sensor Validation , 2013 .

[6]  Kjell Gundersen,et al.  Comparison of inherent optical properties as a surrogate for particulate matter concentration in coastal waters , 2009 .

[7]  Robert H. Stavn,et al.  Correcting the errors from variable sea salt retention and water of hydration in loss on ignition analysis: Implications for studies of estuarine and coastal waters , 2009 .

[8]  J. C. Goldman,et al.  Susceptibility of some marine phytoplankton species to cell breakage during filtration and post-filtration rinsing , 1985 .

[9]  G. Neukermans Optical in situ and geostationary satellite-borne observations of suspended particles in coastal waters , 2012 .

[10]  Reinold Pasterkamp,et al.  REVAMP- regional validation of meris chlorophyll products in North sea coastal waters , 2004 .

[11]  R. Kiene,et al.  Filter-type and sample handling affect determination of organic substrate uptake by bacterioplankton , 1999 .

[12]  K.,et al.  NOT TO BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHORS International Council for the Exploration of the Sea , 2003 .

[13]  T. Parsons,et al.  A practical handbook of seawater analysis , 1968 .

[14]  Mark R. Miller,et al.  Ocean Optics Protocols For Satellite Ocean Color Sensor Validation, Revision 4, Volume III: Radiometric Measurements and Data Analysis Protocols , 2003 .

[15]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .

[16]  David McKee,et al.  In situ variability of mass‐specific beam attenuation and backscattering of marine particles with respect to particle size, density, and composition , 2012 .

[17]  A. Sciandra,et al.  Determining Size Distributions and Composition of Particles Suspended in Water: A New SEM-EDS Protocol with Validation and Comparison to Other Methods , 2012 .

[18]  D. York Least-squares fitting of a straight line. , 1966 .

[19]  Robert R. Bidigare,et al.  On the chlorophyll a retention properties of glass‐fiber GF/F filters , 1995 .

[20]  R. W. Sheldon,et al.  Retention of Marine Particles by Screens and FILTERS1 , 1969 .

[21]  Dariusz Stramski,et al.  The role of seawater constituents in light backscattering in the ocean , 2004 .